After checking the Use hardware acceleration (as shown above by Jeff), as the checkbox says you have to restart Rainmeter (not the computer). Close it completely and start it again. If you don't do this, the setting won't be applied.

Same here.
windows 7 64 bit core i7 Intel HD 4600.
version 4.2 - 5% of cpu (lot of heavy skins)
v 4.3 - 40% cpu and very slow work of program.
Also I noticed that "DbgUiRemoteBreakin" threads of rainmeter also use lot of CPU as well as main thread.
After turning Hardware Acceleration on in Settings CPU usage lowered to 12%, but animations of widgets are laggy.